/**
 * Note: It must be the first filter defined in the post process chain.
 *
 * Shader code downloaded from: https://github.com/mitsuhiko/webgl-meincraft/blob/master/assets/shaders/fxaa.glsl
 */
GG.FxaaScreenFilter = function (argument) {	
};

GG.FxaaScreenFilter.prototype = new GG.ScreenFilter();
GG.FxaaScreenFilter.prototype.constructor = GG.FxaaScreenFilter;

GG.PostProcessChain.registerScreenFilter('fxaa', GG.FxaaScreenFilter);

GG.FxaaScreenFilter.prototype.inject = function (programSource) {
	programSource.uniform('vec2', 'u_viewportSize')
		.addDecl('fxaa', this.getFxaaGlsl())
		.addMainBlock(" color = applyFXAA(v_texCoords, u_sourceTexture);");
};

GG.FxaaScreenFilter.prototype.getFxaaGlsl = function (argument) {
	return ["#ifndef FXAA_GLSL_INCLUDED",
		"#define FXAA_GLSL_INCLUDED",
		"",
		"/* Basic FXAA implementation based on the code on geeks3d.com with the",
		"   modification that the texture2DLod stuff was removed since it's",
		"   unsupported by WebGL. */",
		"",
		"#define FXAA_REDUCE_MIN   (1.0/ 128.0)",
		"#define FXAA_REDUCE_MUL   (1.0 / 8.0)",
		"#define FXAA_SPAN_MAX     8.0",
		"",
		"vec4 applyFXAA(vec2 fragCoord, sampler2D tex)",
		"{",
		"    vec4 color;",
		"    vec2 inverseVP = vec2(1.0 / u_viewportSize.x, 1.0 / u_viewportSize.y);",
		"    vec3 rgbNW = texture2D(tex, fragCoord + vec2(-1.0, -1.0) * inverseVP).xyz;",
		"    vec3 rgbNE = texture2D(tex, fragCoord + vec2(1.0, -1.0) * inverseVP).xyz;",
		"    vec3 rgbSW = texture2D(tex, fragCoord + vec2(-1.0, 1.0) * inverseVP).xyz;",
		"    vec3 rgbSE = texture2D(tex, fragCoord + vec2(1.0, 1.0) * inverseVP).xyz;",
		"    vec3 rgbM  = texture2D(tex, fragCoord).xyz;",
		"    vec3 luma = vec3(0.299, 0.587, 0.114);",
		"    float lumaNW = dot(rgbNW, luma);",
		"    float lumaNE = dot(rgbNE, luma);",
		"    float lumaSW = dot(rgbSW, luma);",
		"    float lumaSE = dot(rgbSE, luma);",
		"    float lumaM  = dot(rgbM,  luma);",
		"    float lumaMin = min(lumaM, min(min(lumaNW, lumaNE), min(lumaSW, lumaSE)));",
		"    float lumaMax = max(lumaM, max(max(lumaNW, lumaNE), max(lumaSW, lumaSE)));",
		"    ",
		"    vec2 dir;",
		"    dir.x = -((lumaNW + lumaNE) - (lumaSW + lumaSE));",
		"    dir.y =  ((lumaNW + lumaSW) - (lumaNE + lumaSE));",
		"    ",
		"    float dirReduce = max((lumaNW + lumaNE + lumaSW + lumaSE) *",
		"                          (0.25 * FXAA_REDUCE_MUL), FXAA_REDUCE_MIN);",
		"    ",
		"    float rcpDirMin = 1.0 / (min(abs(dir.x), abs(dir.y)) + dirReduce);",
		"    dir = min(vec2(FXAA_SPAN_MAX, FXAA_SPAN_MAX),",
		"              max(vec2(-FXAA_SPAN_MAX, -FXAA_SPAN_MAX),",
		"              dir * rcpDirMin)) * inverseVP;",
		"      ",
		"    vec3 rgbA = 0.5 * (",
		"        texture2D(tex, fragCoord  + dir * (1.0 / 3.0 - 0.5)).xyz +",
		"        texture2D(tex, fragCoord  + dir * (2.0 / 3.0 - 0.5)).xyz);",
		"    vec3 rgbB = rgbA * 0.5 + 0.25 * (",
		"        texture2D(tex, fragCoord  + dir * -0.5).xyz +",
		"        texture2D(tex, fragCoord  + dir * 0.5).xyz);",
		"",
		"    float lumaB = dot(rgbB, luma);",
		"    if ((lumaB < lumaMin) || (lumaB > lumaMax))",
		"        color = vec4(rgbA, 1.0);",
		"    else",
		"        color = vec4(rgbB, 1.0);",
		"    return color;",
		"}",
		"",
		"#endif"].join('\n');
};

GG.FxaaScreenFilter.prototype.setUniforms = function (program) {
};
